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A Step Toward an Invisibility Cloak
Technology Review has a writeup on the latest advance in the lab towards an invisibility cloak made of metamaterials, described this week in Science. We've been following this technology since the beginning. The breakthrough is software that lets researchers design materials that are both low-loss and wideband. "The cloak that the researchers built works with wavelengths of light ranging from about 1 to 18 gigahertz — a swath as broad as the visible spectrum. No one has yet made a cloaking device that works in the visible spectrum, and those metamaterials that have been fabricated tend to work only with narrow bands of light. But a cloak that made an object invisible to light of only one color would not be of much use. Similarly, a cloaking device can't afford to be lossy: if it lets just a little bit of light reflect off the object it's supposed to cloak, it's no longer effective. The cloak that Smith built is very low loss, successfully rerouting almost all the light that hits it."
Direct link please!
http://www.technologyreview.com/computing/21971/?a=f
Garbage javascript broke for me and the page didn't get past a white page.
"works with wavelengths of light ranging from about 1 to 18 gigahertz"
frequency is in hertz.
wavelength is a length, so it will be in meters or feet or inches or volkswagen bugs.
that is all. </pedantic>
"The value of a man resides in what he gives,
and not in what he is capable of receiving."
--Albert Einstein
1-18 ghz is way way broader than a very thin swat of visible light. Just looking at the spectra should show it. Mod me actually uninformative or overrater.
C. Sagan : A demon haunted world:
http://www.amazon.com/gp/product/0345409469/
visit randi.org
I don't see why they're overdoing this so much. I've been able to become invisible for a long time--all I have to do is cover my eyes!
Try it today!
(disclaimer: i work in electromagnetics and have a bone to pick with metamaterials)
in general those who research metamaterials are regarded as roughly at the same level as Roswell conspiracy theorists. the math to come up with the idea is simple (don't bother with Maxwell, just use Snell's Law) but any substance that has the required negative permittivity or permeability to have zero reflection at one band is decidedly NOT negative in another. that, boys and girls, is the physics of the matter. (pun)
in practice boards of metamaterial are built by growing/printing funny shapes that create effectively negative physical quantities. most (if not all) metamaterial designs are arrived at through genetic algorithms and involve very little understanding of why they work. the process is 1. "hey computer, find me some negative effective epsilon over this frequency range" 2. walk away 3. publish whatever the computer said 4. (optional) try to build it and realize you have no idea what is going on.
additionally, often left out of these wonderous 'science' articles is the effect of polarization on transmittance. the may claim 18:1 BW in this article, but this is most likely only for linearly polarized, normal incidence waves.
for the DoD's sake, let's hope that Random Future Enemy has only a single band radar station looking directly at the incoming attacker.
ugh.
Bah, "ain't" is a perfectly valid contraction for "am not", and has been since at least 1706. (See http://www.etymonline.com/index.php?search=ain't&searchmode=none) Proscriptionists object to it largely because it's often used for "is not", or "are not", which was seen as somehow "perverting" the English language.
In fact, though, "ain't" has been used that way since at least the 19th century.
About the worst that you can say of "ain't" is that it's inappropriate for a formal register, but so are most contractions.
Cheers,
Your Friendly Neighborhood Pedant
We may not imagine how our lives could be more frustrating and complex—but Congress can. – Cullen Hightower
Except that full concealment or invisibility only grants you 50% miss chance and you can't gain more than that.
Learn the rules!
7000 -> f = lambda/c -> 4.28275E+14
5000 -> f = lambda/c -> 5.99585E+14
Difference -> 1.713E+14 Hz -> 1.713E5 GHZ
About 171,000 GHZ not 17
For those of you who have wondered where the "robe and wizard hat" thing came from:
http://bash.org/?104383
i'd hit it so hard, if you pulled me out you'd be the king of britain [bash.org]
Not if the other person has the feat blindfight.